I don't know how diastolic function can be assessed with a thalium stress test. The spacial resolution is certainly not sufficient to evaluate this on a routine basis. It may simply be related to some increased count uptake in the LV, which may be correlated with LVH which is associated with diastolic dysfunction. I don't think thalium can directly evaluate diastolic function of the LV.
I'm not a MD. , but I think this might be referred to as diastolic dysfunction, I think its a fairly common finding with high blood pressure.I think medications that reduce hypertension can be helpful in most cases.